U.S. patent application number 12/520660 was filed with the patent office on 2010-02-04 for composition for forming transparent electroconductive film, transparent electroconductive film, and display.
This patent application is currently assigned to MITSUBISHI MATERIALS ELECTRONIC CHEMICALS CO., LTD. Invention is credited to Kenji Hayashi, Hiroshi Ikeda, Daigou Mizoguchi, Masaaki Murakami, Masamichi Murota, Masato Murouchi, Kunio Omura, Hirotoshi Umeda.
Application Number | 20100025638 12/520660 |
Document ID | / |
Family ID | 39562217 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100025638 |
Kind Code |
A1 |
Murota; Masamichi ; et
al. |
February 4, 2010 |
COMPOSITION FOR FORMING TRANSPARENT ELECTROCONDUCTIVE FILM,
TRANSPARENT ELECTROCONDUCTIVE FILM, AND DISPLAY
Abstract
A composition includes a binder component and a conductive
powder and a high-refractive-index powder both dispersed in the
binder component, wherein the conductive powder includes 0.1 to 30
mass % of a tin hydroxide powder and 70 to 99.9 mass % of other
conductive powder. The composition enables to form a transparent
conductive film having excellent scratch resistance, excellent
antistatic properties, an extremely high visible light
transmittance and a controllable refractive index. Also described
is the transparent conductive film. Further described is a display
having the transparent conductive film on the display surface.
Inventors: |
Murota; Masamichi;
(Akita-shi, JP) ; Umeda; Hirotoshi; (Akita-shi,
JP) ; Ikeda; Hiroshi; (Akita-shi, JP) ; Omura;
Kunio; (Akita-shi, JP) ; Murouchi; Masato;
(Otawara-shi, JP) ; Hayashi; Kenji; (Otawara-shi,
JP) ; Mizoguchi; Daigou; (Otawara-shi, JP) ;
Murakami; Masaaki; (Otawara-shi, JP) |
Correspondence
Address: |
YOUNG & THOMPSON
209 Madison Street, Suite 500
Alexandria
VA
22314
US
|
Assignee: |
MITSUBISHI MATERIALS ELECTRONIC
CHEMICALS CO., LTD
AKITA-SHI
JP
MITSUBISHI MATERIALS CORPORATION
TOKYO
JP
DAI NIPPON TORYO CO., LTD.
OSAKA-SHI
JP
|
Family ID: |
39562217 |
Appl. No.: |
12/520660 |
Filed: |
June 6, 2007 |
PCT Filed: |
June 6, 2007 |
PCT NO: |
PCT/JP2007/061473 |
371 Date: |
June 22, 2009 |
Current U.S.
Class: |
252/512 ;
252/519.51; 252/520.1 |
Current CPC
Class: |
H01B 1/14 20130101; C09D
5/24 20130101; H01B 1/08 20130101 |
Class at
Publication: |
252/512 ;
252/520.1; 252/519.51 |
International
Class: |
H01B 1/08 20060101
H01B001/08; H01B 1/02 20060101 H01B001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2006 |
JP |
2006-350554 |
Claims
1-10. (canceled)
11. A composition for forming transparent conductive film,
characterized by comprising a binder component, and a conductive
powder and a high-refractive index powder which are dispersed in
the binder component, wherein the conductive powder is formed of
tin hydroxide powder in an amount of 0.1 to 30 mass % and a
conductive powder other than tin hydroxide powder in an amount of
70 to 99.9 mass %.
12. A composition for forming transparent conductive film as
described in claim 11, wherein the tin hydroxide powder contains,
as a dopant, at least one species selected from among P, Al, In,
Zn, and Sb.
13. A composition for forming transparent conductive film as
described in claim 12, wherein the amount of dopant which is at
least one species selected from among P, Al, In, Zn, and Sb is 0.1
to 20 at % with respect to the total amount of dopant and Sn.
14. A composition for forming transparent conductive film as
described in claim 11, wherein the conductive powder other than tin
hydroxide powder is formed of at least one species selected from
the group consisting of zinc oxide, tin oxide, ATO, ITO, indium
oxide, zinc aluminum oxide, antimony pentoxide, and zinc
antimonate.
15. A composition for forming transparent conductive film as
described in claim 12, wherein the conductive powder other than tin
hydroxide powder is formed of at least one species selected from
the group consisting of zinc oxide, tin oxide, ATO, ITO, indium
oxide, zinc aluminum oxide, antimony pentoxide, and zinc
antimonate.
16. A composition for forming transparent conductive film as
described in claim 11, wherein the high-refractive index powder is
formed of at least one species selected from the group consisting
of zirconium oxide, titanium oxide, and cerium oxide.
17. A composition for forming transparent conductive film as
described in claim 15, wherein the high-refractive index powder is
formed of at least one species selected from the group consisting
of zirconium oxide, titanium oxide, and cerium oxide.
18. A composition for forming transparent conductive film as
described in claim 11, wherein the ratio by mass represented by
conductive powder/high-refractive index powder is 30/70 to
90/10.
19. A composition for forming transparent conductive film as
described in claim 17, wherein the ratio by mass represented by
conductive powder/high-refractive index powder is 30/70 to
90/10.
20. A composition for forming transparent conductive film as
described in claim 11, wherein the ratio by mass represented by
(conductive powder+high-refractive index powder)/binder component
is 5/95 to 95/5.
21. A composition for forming transparent conductive film as
described in claim 19, wherein the ratio by mass represented by
(conductive powder+high-refractive index powder)/binder component
is 5/95 to 95/5.
22. A transparent conductive film, characterized in that the film
is produced by applying a composition for forming transparent
conductive film as recited in claim 11 through coating or printing
and curing the applied composition.
23. A transparent conductive film, characterized in that the film
is produced by applying a composition for forming transparent
conductive film as recited in claim 20 through coating or printing
and curing the applied composition.
24. A transparent conductive film, characterized in that the film
is produced by applying a composition for forming transparent
conductive film as recited in claim 21 through coating or printing
and curing the applied composition.
25. A transparent conductive film as described in claim 22, which
has a surface resistivity of 10.sup.6 to 10.sup.11 .OMEGA./square,
a light transmittance of 85% or higher, a haze of 1.5% or lower,
and a refractive index of 1.55 to 1.90.
26. A transparent conductive film as described in claim 23, which
has a surface resistivity of 10.sup.6 to 10.sup.11 .OMEGA./square,
a light transmittance of 85% or higher, a haze of 1.5% or lower,
and a refractive index of 1.55 to 1.90.
27. A transparent conductive film as described in claim 24, which
has a surface resistivity of 10.sup.6 to 10.sup.11 .OMEGA./square,
a light transmittance of 85% or higher, a haze of 1.5% or lower,
and a refractive index of 1.55 to 1.90.
28. A display characterized by having, on a screen thereof, a
transparent conductive film as recited in claim 22.
29. A display characterized by having, on a screen thereof, a
transparent conductive film as recited in claim 23.
30. A display characterized by having, on a screen thereof, a
transparent conductive film as recited in claim 27.
Description
TECHNICAL FIELD
[0001] The present invention relates to a composition for forming
transparent conductive film, to a transparent conductive film, and
to a display having a transparent conductive film on a screen
thereof. More particularly, the invention relates to a composition
which can form a transparent conductive film by applying the
composition on the surface of any of various transparent
substrates, particularly on a display screen of an LCD, a plasma
display, etc., through coating or printing, and then curing the
applied composition; to a transparent conductive film; and to a
display having a transparent conductive film on a screen thereof.
The formed transparent conductive film exhibits remarkably
excellent scratch resistance and excellent antistatic effect and
has very high visible light transmittance.
BACKGROUND ART
[0002] Generally, image-display devices and optical apparatuses
such as a liquid crystal display and a cathode-ray tube display are
provided with an antireflection film. The anti-reflection film must
have not only high transparency and low reflectivity but also
scratch resistance and a function of preventing deposition of
foreign matter (e.g., dust) on the film. Therefore, high
transparency, high refractive index, excellent scratch resistance,
and excellent antistatic property are required for a
high-refractive index layer included in the anti-reflection
film.
[0003] One possible means for imparting antistatic property to a
high-refractive index layer of the anti-reflection film is addition
of a surfactant, a conductive polymer, or a conductive metal oxide
to the high-refractive index layer. From the viewpoint of attaining
long-term antistatic effect and high refractive index of the formed
film, in a generally employed technique, conductive metal oxide
microparticles are used. Generally, in the production of a
high-refractive index layer of the anti-reflection film, a coating
material containing one or more species of microparticles of
high-refractive index metal oxides and a binder is employed (see,
for example, Patent Documents 1, 2, and 3).
[Patent Document 1]
[0004] Japanese Patent Application laid-Open (kokai) No.
11-181335
[Patent Document 2]
[0005] Japanese Patent Application laid-Open (kokai) No.
2006-124406
[Patent Document 3]
[0006] Japanese Patent Application laid-Open (kokai) No.
2006-188588
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0007] However, when the amount of metal oxide microparticles in
the high-refractive index layer of the anti-reflection film is
increased in order to enhance the refractive index of the
high-refractive index layer, the resin content decreases with
increasing amount of metal oxide microparticles. As a result, the
scratch resistance of the high-refractive index layer; i.e., the
scratch resistance of the anti-reflection film, decreases. In
contrast, when the amount of metal oxide microparticles in the
high-refractive index layer is reduced, the conductivity and
refractive index of the high-refractive index layer of the
anti-reflection film decrease. Therefore, difficulty is encountered
in producing transparent conductive film having satisfactory
characteristics including scratch resistance, high transparency,
high refractive index, and antistatic property.
[0008] The present invention has been accomplished to solve the
aforementioned problems, and an object of the invention is to
provide a composition which can form a transparent conductive film
that exhibits remarkably excellent scratch resistance and excellent
antistatic effect and has very high visible light transmittance and
which can impart a desired refractive index to the film. Another
object of the invention is to provide such a transparent conductive
film. Still another object of the invention is to provide a display
having such a transparent conductive film on a screen thereof
Means for Solving the Problems
[0009] The present inventors have carried out extensive studies in
order to attain the above objects and have found that a composition
which can form a transparent conductive film that exhibits
remarkably excellent scratch resistance, excellent antistatic
effect, and has very high visible light transmittance and which can
impart a desired refractive index to the film can be obtained from
a composition for forming transparent conductive film including a
binder component, and a conductive powder and a high-refractive
index powder which are dispersed in the binder component, wherein
the conductive powder is formed of a specific amount of tin
hydroxide powder and a conductive powder other than tin hydroxide
powder. The present invention has been accomplished on the basis of
this finding.
[0010] Accordingly, the present invention provides a composition
for forming transparent conductive film, characterized by
comprising a binder component, and a conductive powder and a
high-refractive index powder which are dispersed in the binder
component, wherein the conductive powder is formed of tin hydroxide
powder in an amount of 0.1 to 30 mass % and a conductive powder
other than tin hydroxide powder in an amount of 70 to 99.9 mass
%.
[0011] The present invention also provides a transparent conductive
film, characterized in that the film is produced by applying a
composition for forming transparent conductive film, through
coating or printing, and curing the applied composition.
[0012] The present invention also provides a display characterized
by having, on a screen thereof, the transparent conductive film
produced from the composition for forming transparent conductive
film.
EFFECTS OF THE INVENTION
[0013] The composition of the present invention for forming
transparent conductive film can provide a transparent conductive
film by applying the composition in the form of coating or ink on a
surface of a substrate through coating or printing, and then curing
the applied composition. The formed transparent conductive film
exhibits remarkably excellent scratch resistance and excellent
antistatic effect, and has very high visible light transmittance,
and the refractive index of the film can be controlled as desired.
Thus, the composition can be applied to a resin substrate having
low heat resistance and to substrates of various shapes, and
transparent conductive film can be continuously produced on a large
scale. Needless to say, such transparent film having a large area
can be readily produced. Through adjusting the relative amount of
the high-refractive index powder incorporated into the composition,
the refractive index of the film can be controlled as desired. In
addition, through modifying film-formation conditions, a
transparent conductive film having excellent transparency,
conductivity, and scratch resistance; e.g., a surface resistivity
of preferably 10.sup.6 to 10.sup.11 .OMEGA./square, more preferably
10.sup.7 to 10.sup.10 .OMEGA./square, a light transmittance of
preferably 85 or higher, a haze of preferably 1.5 or lower, and a
refractive index of 1.55 to 1.90 can be produced. Thus, the
composition of the present invention for forming transparent
conductive film can be employed in a variety of fields including a
transparent electrode of a liquid crystal display, window material
for solar cells, infrared-ray-reflecting film, antistatic film,
touch panels, plane-shape heaters, and electrophotographic
recording, and exhibits excellent performance in the above
fields.
BEST MODES FOR CARRYING OUT THE INVENTION
[0014] In the composition of the present invention for forming
transparent conductive film, tin hydroxide powder and a
high-refractive index powder are dispersed in the binder component,
wherein the conductive powder is formed of tin hydroxide powder in
an amount of 0.1 to 30 mass % and a conductive powder other than
tin hydroxide powder in an amount of 70 to 99.9 mass %. The tin
hydroxide powder employed in the invention may be powder of tin
hydroxide itself or powder of tin hydroxide containing, as a
dopant, at least one species selected from among P, Al, In, Zn, and
Sb. Such tin hydroxide powders may be used singly or in combination
of two or more species.
[0015] The tin hydroxide powder employable in the present invention
may be a commercial product thereof or produced through a known
method (e.g. neutralizing an acidic solution in which tin chloride
is dissolved with an alkali, to thereby co-precipitate a hydroxide,
and drying the co-precipitate).
[0016] The tin hydroxide powder which contains at least one species
selected from among P, Al, In, Zn, and Sb as a dopant and which can
be employed in the present invention is commercially available.
Alternatively, the doped tin hydroxide powder may be produced
through a known technique: for example, neutralizing an acidic
solution in which phosphorus chloride and tin chloride are
dissolved with an alkali, to thereby co-precipitate phosphorus/tin
hydroxide, and drying the co-precipitate. In the tin hydroxide
powder containing at least one species selected from among P, Al,
In, Zn, and Sb as a dopant, the amount of dopant with respect to
(dopant+Sn) is preferably 0.1 to 20 at %, more preferably 1 to 15
at %. When the amount of dopant is less than 0.1 at %, the effect
of dopant is insufficient, whereas when the amount of dopant is in
excess of 20 at %, the dopant-containing tin hydroxide particles
generally have high electrical resistance, thereby reducing the
conductivity of the formed conductive film.
[0017] According to the present invention, the tin hydroxide
powder, synergistically with a conductive powder other than tin
hydroxide powder and a high-refractive index powder, enhances film
strength to increase scratch resistance without reducing the
conductivity of the formed film. In the present invention, the
relative amount of tin hydroxide powder in the conductive powder is
preferably 0.1 to 30 mass %, more preferably 1 to 20 mass %. When
the relative amount of tin hydroxide powder in the conductive
powder is less than 0.1 mass %, the formed film has unsatisfactory
scratch resistance, whereas when the relative amount of tin
hydroxide powder is in excess of 30 mass %, the formed film
exhibits an enhanced transmittance but reduced scratch resistance
due to the excessive amount of tin hydroxide.
[0018] In the present invention, a conductive powder other than tin
hydroxide powder may be formed of zinc oxide, tin oxide, ATO, ITO,
indium oxide, zinc aluminum oxide, antimony pentoxide, and zinc
antimonate. Such conductive powders other than tin hydroxide powder
may be used singly or in combination of two or more species.
[0019] In the present invention, the high-refractive index powder
is incorporated into the composition in order to control the
refractive index of the formed transparent conductive film. Thus,
the high-refractive index powder employed preferably has a
refractive index of 1.8 to 3.0. Note that the refractive index of a
powder is an intrinsic value to the powder, and such refractive
index values are disclosed in many references. When the powder
having a refractive index less than 1.8 is employed, a film having
high refractive index cannot be formed, whereas when a powder
having a refractive index in excess of 3.0 is employed, the
transparency of the formed film tends to decrease. No particular
limitation is imposed on the type of the high-refractive index
powder of the present invention, so long as the objects of the
invention can be attained, and known products including commercial
products may be used. Examples of such powders include metal oxides
such as zirconium oxide (refractive index n=2.4), titanium oxide
(n=2.76), and cerium oxide (n=2.2).
[0020] When each of the tin hydroxide powder, the tin hydroxide
powder containing, as a dopant, at least one species selected from
among P, Al, In, Zn, and Sb, the conductive powder other than tin
hydroxide powder, and high-refractive index powder has a mean
primary particle size of 0.2 .mu.m or less, a transparent
conductive film can be produced. However, when the mean primary
particle size is in excess of 0.2 .mu.m, the transparency of the
formed film tends to decrease. Therefore, the tin hydroxide powder
is preferably formed of ultra-microparticles having a mean primary
particle size of 0.2 .mu.m or less. When the transparency of the
produced transparent film is not an important factor for uses of
the film, tin hydroxide powder having a particle size greater than
0.2 .mu.m may also be employed. The compact of the conductive
powder preferably has a resistivity of 1.times.10.sup.9 .OMEGA.cm
or less.
[0021] In the composition. of the present invention for forming
transparent conductive film, the ratio by mass of employed
conductive powder to high-refractive index powder (conductive
powder/high-refractive index powder) is preferably 30/70 to 90/10,
more preferably 35/65 to 85/15. When the amount of conductive
powder as reduced to the above ratio by mass is less than 30/70,
the formed film generally has a high refractive index but poor
conductivity. In contrast, when the amount of conductive powder as
reduced to the above ratio by mass is in excess of 90/10, the
formed film has good conductivity but generally fails to have a
target refractive index.
[0022] In the composition of the present invention for forming
transparent conductive film, the ratio by mass of (conductive
powder+high-refractive index powder) to binder component
[(conductive powder+high-refractive index powder)/binder component]
is preferably 5/95 to 95/5, more preferably 20/80 to 90/10, most
preferably 30/70 to 85/15. When the total amount of conductive
powder and high-refractive index powder as reduced to the above
ratio by mass is less than 5/95, the formed film generally has
sufficient transparency but poor conductivity. In contrast, when
the total amount of conductive powder and high-refractive index
powder as reduced to the above ratio by mass is in excess of 95/5,
dispersibility of powder is impaired, and the formed conductive
film generally has poor transparency, adhesion to a substrate, and
film characteristics.
[0023] In the composition of the present invention for forming
transparent conductive film, no particular limitation is imposed on
the binder component so long as the binder component can be
dissolved in a solvent employed, can disperse conductive powder and
high-refractive index powder, and can bind the conductive powder
and the high-refractive index powder to form transparent conductive
film. Any of the binder components which are generally employed in
coating materials may be used. In the present invention, the binder
component is preferably an actinic-radiation-curable binder
component.
[0024] Examples of the binder component include alkyd resin,
polyester resin, unsaturated polyester resin, polyurethane resin,
acrylic resin, epoxy resin, phenolic resin, vinyl resin, silicone
resin, fluoro-resin, phthalate resin, amino resin, polyamide resin,
polyacryl-silicone resin, melamine resin, urea resin, and modified
species thereof. These binder resins may be used singly or in
combination of two or more species.
[0025] If required, the binder component may further contain a
cross-linking agent. Any cross-linking agent having, in a molecule
thereof, two or more reactive functional groups such as a basic
functional group (e.g., amino group), a neutral functional group
(e.g., OH group), an acidic functional group (e.g., carboxyl
group), or an isocyanate group may be employed.
[0026] The binder component may be a radical-polymerizable monomer.
So long as the monomer has a radical-polymerizable unsaturated
group (.alpha.,.beta.-ethylenic unsaturated group), any monomer
having a basic functional group (e.g., amino group), a neutral
functional group (e.g., OH group), an acidic functional group
(e.g., carboxyl group), or no such functional group may be
employed.
[0027] Examples of the actinic-radiation-curable binder component
which may be employed in the composition of the present invention
for forming transparent conductive film include acrylate compounds
and methacrylate compounds. Hereinafter, acrylate compounds and
methacrylate compounds are collectively referred to as
(meth)acrylate compounds.
[0028] In addition to the above-mentioned (meth)acrylate compounds,
examples of the actinic-radiation-curable binder component which
may be employed in the composition of the present invention for
forming transparent conductive film further include
radical-polymerizable monomers and/or oligomers. No particular
limitation is imposed on the radical-polymerizable monomers, and
any such monomers may be employed so long as the monomers each
having a radical-polymerizable unsaturated group
(.alpha.,.beta.-ethylenic unsaturated group). Examples of such
monomers include monomers each having a basic functional group such
as an amino group, monomers each having a neutral functional group
such as an OH group, monomers each having an acidic functional
group such as a carboxyl group, and monomers each having no such a
functional group.
[0029] Specific examples of radical-polymerizable monomers include
non-(meth)acrylate radical-polymerizable monomers such as stryrene,
vinyltoluene, vinyl acetate, N-vinylpyrrolidone, acrylonitrile, and
allyl alcohol; mono-functional (meth)acrylates such as methyl
(meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl
(meth)acrylate, tetrahydrofurfuryl (meth)acrylate,
N-vinylpyrrolidone, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl
(meth)acrylate, polyethylene glycol mono(meth)acrylate,
methoxy-polyethylene glycol mono(meth)acrylate, polypropylene
glycol mono (meth)acrylate, polyethylene glycol polypropylene
glycol mono(meth)acrylate, polyethylene glycol polytetramethylene
glycol mono(meth)acrylate, and glycidyl (meth)acrylate;
bi-functional (meth)acrylates such as ethylene glycol
di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene
glycol di(meth)acrylate, tetraethylene glycol di(meth) acrylate,
polyethylene glycol di(meth)acrylate, polypropylene glycol
di(meth)acrylate, neopentyl glycol di(meth)acrylate, allyl
di(meth)acrylate, bisphenol A di(meth)acrylate, ethylene
oxide-modified bisphenol A di(meth)acrylate, polyethylene
oxide-modified bisphenol A di(meth)acrylate, ethylene
oxide-modified bisphenol S di(meth)acrylate, bisphenol S
di(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,3-butylene
glycol di(meth)acrylate; and (meth)acrylates having 3 or more
functionalities such as trimethylolpropane tri(meth)acrylate,
glycerol tri(meth)acrylate, pentaerythritol tri(meth)acrylate,
pentaerythritol tetra(meth)acrylate, ethylene-modified
trimethylolpropane tri(meth)acrylate, and dipentaerythritol
hexa(meth)acrylate.
[0030] Specific examples of radical-polymerizable oligomers include
prepolymers each having at least one (meth)acryloyl group such as
polyester (meth)acrylate, polyurethane (meth)acrylate, epoxy
(meth)acrylate, polyether (meth)acrylate, oligo (meth)acrylate,
alkyd (meth)acrylate, polyol (meth)acrylate, and silicone
(meth)acrylate. Of these, polyester (meth)acrylate, epoxy
(meth)acrylate, and polyurethane (meth)acrylate are particularly
preferred.
[0031] In order to impart advantageous actinic-radiation curability
to the composition of the present invention for forming transparent
conductive film, a polymerization initiator (photo-sensitizer) is
preferably incorporated into the composition. Through incorporation
of the initiator, the composition can be cured with a small dose of
an actinic-radiation. However, since the composition of the present
invention for forming transparent conductive film can also be cured
by heat, an appropriate radical polymerization initiator (e.g.,
azobis(isobutyronitrile) may be incorporated into the composition
as a thermally curing agent instead of the photo-sensitizer.
[0032] Examples of the polymerization initiator which allows the
resin composition to be actinic-radiation-curable include
1-hydroxycyclohexyl phenyl ketone, benzophenone, benzyl dimethyl
ketone, benzoin methyl ether, benzoin ethyl ether,
p-chlorobenzophenone, 4-benzoyl-4-methyldiphenyl sulfide,
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and
2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1. These
polymerization initiators may be used singly or in combination of
two or more species. The polymerization initiator is preferably
employed in an amount of 0.1 to 20 parts by mass, more preferably 1
to 15 parts by mass with respect to 100 parts by mass of the binder
component.
[0033] So long as the objects of the invention are not impaired,
other customary employed additives may be incorporated into the
composition of the invention for forming transparent conductive
film. Examples of such additives include a polymerization
inhibitor, a curing catalyst, an anti-oxidant, and a leveling
agent.
[0034] In the composition of the present invention for forming
transparent conductive film, no particular limitation is imposed on
the solvent so long as the solvent can dissolve or disperse the
binder component, can disperse desired conductive powder and
high-refractive index powder, and does not corrode a substrate. Any
solvent which is generally employed in coating materials may be
used. Examples of the solvent which may be used in the invention
include hydrocarbons such as hexane, heptane, cyclohexane, toluene,
and m-xylene; halohydrocarbons such as tetrachloromethane and
trichloroethylene; ketones such as acetone, methyl ethyl ketone,
methyl isobutyl ketone, diisobutyl ketone, isophorone, and
cyclohexanone; ethers such as diethyl ether, dioxane, and
tetrahydrofuran; esters such as ethyl acetate, butyl acetate, and
isoamyl acetate; alcohols such as methanol, ethanol, n-propanol,
isopropanol, n-butanol, 2-butanol, n-pentanol, 2-ethylhexanol,
cyclohexanol, diacetone alcohol, ethylene glycol, propylene glycol,
diethylene glycol, and glycerin; ether/alcohols and ether/esters
such as ethylene glycol monoethyl ether, ethylene glycol monobutyl
ether, ethylene glycol monoethyl ether acetate, propylene glycol
monoethyl ether, propylene glycol monopropyl ether, propylene
glycol monobutyl ether, and propylene glycol monomethyl ether
acetate; and mixtures thereof. The amount of solvent is adjusted
such that a composition (final product) prepared by dispersing
desired components of conductive powder, high-refractive index
powder, and light-transmission-ensuring microparticles has a
viscosity suitable for coating or printing. The composition of the
present invention for forming transparent conductive film
preferably has a viscosity of 2 to 10,000 cps (E-type viscometer:
20.degree. C.).
[0035] The composition of the present invention for forming
transparent conductive film may be produced through, for example,
dispersing conductive powder and high-refractive index powder in
the binder component solution which has been optionally diluted
with organic solvent. Alternatively, the composition may be
produced through dispersing conductive powder and high-refractive
index powder in an organic solvent and adding the binder component
to the dispersion. Needless to say, the composition may also be
produced through mixing together the binder component, desired
components of conductive powder, high-refractive index powder, and
light-transmission-ensuring microparticles, and an organic solvent
in a single operation, to thereby form a dispersion. The dispersion
process may be carried out through a routine method by means of a
paint shaker, a ball mill, a sand mill, a centri-mill, a three-roll
mill, or a similar apparatus. Needless to say, dispersion may be
carried out through a generally performed stirring process.
[0036] Examples of the material of the substrate to which the
composition of the present invention for forming transparent
conductive film is applied so as to form transparent conductive
film include synthetic resins, glass materials, and ceramic
materials, which are widely employed in variety of fields including
electrics and electronics. The substrate may have any shape such as
sheet, film, or plate. Non-limitative specific examples of
synthetic resins include polyethylene, polypropylene,
polycarbonate, acrylic resin, methacrylic resin, poly(vinyl
chloride), polyester resin, polyamide resin, and phenolic
resin.
[0037] Application (coating or printing) of the composition of the
present invention for forming transparent conductive film onto a
substrate may be performed through a routine method such as roll
coating, spin coating, or screen printing. Subsequently, when the
binder component is not actinic-radiation-curable, if required, the
applied composition is heated to evaporate solvent, to thereby dry
and cure the coating film. When the binder component is
actinic-radiation-curable, if required, the applied composition is
heated to evaporate solvent, and the coating film is dried
Subsequently, the coating film is irradiated with actinic radiation
(UV ray or electron beam). Examples of the source of actinic
radiation which may be employed in the invention include UV sources
such as a low-pressure mercury lamp, a high-pressure mercury lamp,
a metal halide lamp, a xenon lamp, an excimer laser, and a dye
layer and an electron beam accelerator. The dose of actinic
radiation is preferably 50 to 3,000 mJ/cm.sup.2 in the case of an
UV ray, and 0.2 to 1,000 .mu.C/cm.sup.2 in the case of electron
beam. By the action of actinic radiation, the binder component is
polymerized, to thereby form a transparent conductive film in which
conductive powder and high-refractive index powder are bound by
resin. Preferably, the transparent conductive film has thickness of
0.1 to 10 .mu.m.
[0038] The transparent conductive film of the present invention
formed, on a substrate, from the composition of the present
invention for forming transparent conductive film has excellent
transparency, conductivity, and scratch resistance; e.g., a surface
resistivity of preferably 10.sup.7 to 10.sup.11 .OMEGA./square,
more preferably 10.sup.7 to 10.sup.10 .OMEGA./square, a light
transmittance of preferably 85% or higher, and a haze of 1.5% or
lower, can be produced. In addition, the refractive index of the
transparent conductive film can be controlled. The transparent
conductive film having such properties can be used as, for example,
a dust-preventive film for use in electrophotographic recording or
an antistatic film. The film may also be employed on a display
screen.
EXAMPLES
[0039] The present invention will next be described in detail by
way of Examples and Comparative Examples. Unless otherwise
specified, in Examples and comparative Examples, the unit "part(s)"
refers to "part(s) by mass." In Examples and Comparative Examples,
the following substances were employed.
<Tin Hydroxide Powder>
[0040] Tin hydroxide powder having a mean primary particle size of
0.05 .mu.m and a resistivity of 1.times.10.sup.7 .OMEGA.cm;
[0041] P-doped Sn(OH).sub.4 powder containing phosphorus as a
dopant, having a P/(Sn+P) of 5.0 at % and being formed of particles
having a mean primary particle size of 0.05 .mu.m and a resistivity
of 5.times.10.sup.7 .OMEGA.cm;
<Conductive Powder Other than Tin Hydroxide Powder>
[0042] ATO having a mean primary particle size of 0.06 .mu.m and a
resistivity of 10 .OMEGA.cm;
[0043] SnO.sub.2 having a mean primary particle size of 0.06 .mu.m
and a resistivity of 300 .OMEGA.cm;
<High-Refractive Index Powder>
[0044] ZrO.sub.2 powder having a refractive index of 2.4;
[0045] TiO.sub.2 powder having a refractive index of 2.76;
<Binder Component>
[0046] KAYARAD TMPTA (trimethylolpropane triacrylate, product of
Nippon Kayaku Co., Ltd.);
[0047] KAYARAD DPHA (dipentaerythritol hexaacrylate, product of
Nippon Kayaku Co., Ltd.);
<Initiator>
[0048] IRGACURE 907
(2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one,
product of Ciba Specialty Chemicals K.K.).
Example 1
[0049] A binder component composed of TMPTA (20 parts) and DPHA (10
parts), ATO powder (37.8 parts), tin hydroxide powder (4.2 parts),
zirconium oxide powder (28 parts), isobutanol (150 parts), and
glass beads (250 parts) were placed in a vessel and kneaded for
five hours by means of a paint-shaker, with the dispersion state
being monitored by means of a particle gauge. After kneading,
IRGACURE 907 (3 parts) was added to the kneaded product, and the
mixture was completely dissolved. Glass beads were removed, to
thereby produce a viscous liquid. Subsequently, the viscous liquid
was applied onto a PET film (thickness: 100 .mu.m, Toyobo A4100) by
means of a roll coater, and organic solvent was evaporated. The
formed coating was irradiated with a UV ray from a high-pressure
mercury lamp at a dose of 500 mJ/cm.sup.2, whereby a transparent
cured coating film having a thickness of 5 .mu.m was formed.
Example 2
[0050] A binder component composed of TMPTA (30 parts), tin
hydroxide powder containing phosphorus as a dopant (70 parts)
isobutanol (solvent) (150 parts), and glass beads (250 parts) were
placed in a vessel and kneaded for five hours by means of a
paint-shaker, with the dispersion state being monitored by means of
a particle gauge. After kneading, IRGACURE 907 (3 parts) serving as
a photopolymerization initiator was added to the kneaded product,
and the mixture was completely dissolved. Glass beads were removed,
to thereby produce a viscous liquid (composition A). Separately,
the procedure of preparing composition A was repeated, except that
ATO powder (70 parts) was used instead of tin hydroxide powder (70
parts), to thereby produce another viscous liquid (composition B).
Also, the procedure of preparing composition A was repeated, except
that zirconium oxide powder (70 parts) was used instead of tin
hydroxide powder (70 parts), to thereby produce another viscous
liquid (composition C). The thus-produced composition A (54 parts),
composition B (6 parts), and composition C (40 parts) were
sufficiently mixed, to thereby prepare a coating liquid.
Subsequently, in a manner similar to that of Experimental Example
1, a transparent cured coating film having a thickness of 5 .mu.m
was formed.
Example 3
[0051] The procedure of Example 2 was repeated, except that TMPTA
(20 parts) and DPHA (10 parts) were used instead of TMPTA (30
parts), and tin hydroxide powder containing no dopant (70 parts)
was used instead of tin hydroxide powder containing phosphorus as a
dopant (70 parts), to thereby produce composition A. Also, the
procedure of Example 2 was repeated, except that SnO.sub.2 powder
(70 parts) was used instead of ATO powder (70 parts), to thereby
produce composition B. Also, the procedure of Example 2 was
repeated, except that titanium oxide (70 parts) was used instead of
zirconium oxide (70 parts), to thereby produce composition C. The
thus-produced composition A (67.5 parts), composition B (7.5
parts), and composition C (25 parts) were sufficiently mixed, to
thereby prepare a coating liquid. Subsequently, in a manner similar
to that of Experimental Example 1, a transparent cured coating film
having a thickness of 5 .mu.m was formed.
Comparative Example 1
[0052] A binder component composed of DPHA (20 parts) and TMPTA (10
parts), tin hydroxide powder (35 parts), zirconium oxide powder (35
parts), isobutanol (solvent) (150 parts), and glass beads (250
parts) were placed in a vessel and kneaded for five hours by means
of a paint-shaker, with the dispersion state being monitored by
means of a particle gauge. After kneading, IRGACURE 907 (3 parts)
was added to the kneaded product, and the mixture was completely
dissolved. Glass beads were removed, to thereby produce a viscous
liquid. Subsequently, the viscous liquid was applied onto a PET
film (thickness 100 .mu.m, Toyobo A4100) by means of a roll coater,
and organic solvent was evaporated. The formed coating was
irradiated with a UV ray from a high-pressure mercury lamp at a
dose of 500 mJ/cm.sup.2, whereby a transparent cured coating film
having a thickness of 5 .mu.m was formed.
Comparative Example 2
[0053] The procedure of Comparative Example 1 was repeated, except
that ATO (35 parts) was used instead of tin hydroxide (35 parts),
to thereby form a transparent cured coating film having a thickness
of 5 .mu.m.
[0054] The total light transmittance (%) and haze (%) of the
transparent cured coating films produced in Examples 1 to 3 and
Comparative Examples 1 and 2 were determined by means of TC-HIII
DPK (product of Tokyo Denshoku Technical Center). These values were
determined when each film was stacked on a substrate. The surface
resistivity (.OMEGA./square) of each film was determined by a
surface resistivity meter (Hiresta IP MCP-HT260, product of
Mitsubishi Chemical Corporation). Scratch resistance was evaluated
visually based on the ratings described hereinbelow. The refractive
index of each of the cured coating films produced in the Examples
and Comparative Examples was determined by means of an Abbe
refractometer DR-M4 (product of Atago) (20.degree. C.) The results
are shown in Table 1.
<Ratings for Scratch Resistance Evaluation>
[0055] The surface of each transparent cured coating film sample
was scratched reciprocally 20 times with steel wool (#0000) at a
load of 200 g. Similarly, the surface of the sample was scratched
reciprocally 20 times with steel wool (#0000) at a load of 1,000 g.
In both cases, the surface state after scratching was visually
evaluated based on the following ratings: [0056] O: no scratches;
[0057] .DELTA.: slightly scratched; and [0058] X: scratched
TABLE-US-00001 [0058] TABLE 1 Examples Comp. Examples 1 2 3 1 2
Conductive powder ATO ATO SnO.sub.2 Sn(OH).sub.4 ATO Sn(OH).sub.4
P-doped Sn(OH).sub.4 Sn(OH).sub.4 High-refractive index powder
ZrO.sub.2 ZrO.sub.2 TiO.sub.2 ZrO.sub.2 ZrO.sub.2 Sn hydroxide
content of 10 10 10 100 0 conductive powder (mass %) Conductive
powder/high-refractive 60/40 60/40 75/25 50/50 50/50 index powder
P/B 70/30 70/30 70/30 70/30 70/30 Transmittance (%) 85 86 87 87 85
Haze (%) 0.8 0.7 0.9 1.0 0.9 Surface resistivity (.OMEGA./square) 6
.times. 10.sup.7 6 .times. 10.sup.7 1 .times. 10.sup.8 4 .times.
10.sup.10 2 .times. 10.sup.8 Scratch 200 g load .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. resistance
1,000 g load .largecircle. .largecircle. .largecircle. X .DELTA.
Refractive index 1.65 1.65 1.72 1.65 1.65
[0059] As is clear from Table 1, when the composition of the
present invention for forming transparent conductive film, the
composition containing tin hydroxide powder, a conductive powder
other than tin hydroxide powder, and high-refractive index powder,
was applied to a substrate (Examples 1 to 3), a transparent
conductive film having remarkably excellent scratch resistance and
excellent transparency and conductivity; e.g., a surface
resistivity of 10.sup.6 to 10.sup.11 .OMEGA./square, a light
transmittance of 85% or higher, and a haze of 1.5% or lower, was
produced, and the refractive index of the film could be controlled.
However, when the conductive powder was formed of solely tin
hydroxide powder (Comparative Example 1) or ATO powder (Comparative
Example 2), the formed transparent film exhibited insufficient
scratch resistance.
* * * * *